Indeed, copy numbers of cell‐free EWSR1‐ETS fusion sequences correlate with patients’ risk factors such as tumor volume, pelvic tumor, and metastatic status, and most EwS patients show a fast reduction of cfDNA levels during treatment, while recurrence of increasing cfDNA levels indicates relapse (Krumbholz et al, 2016). This evidence concerns the gene EWSR1 and neoplasm.